This report presents the summary of the model results after calibration of activity-based model sub-models and validation of highway assignment and transit assignment procedures. The first sub-section External Station Validation compares the model forecasted trips passing through the external stations against the corresponding targets prepared in an earlier report (ExternalStationComposition.html). The Highway Validation section provides the summary of highway validation by comparing model assigned volume against observed roadway counts. The Transit Validation sections compares the boardings predicted by model against the observed boardings. The last section looks at the vehicle miles travelled (VMT) by all the trips; within, into and out of the Lake Tahoe modeling region.

External Station Validation

The external stations trip composition calibration results are shown in the table below. The creation of the target trip numbers is described in detail in the report ExternalStationComposition.html. The calibration of work trips; for both residents and external workers, has also been detailed in the report ExternalWorkerCalibration.html.

Table 1: External trips by type and gate: Targets
External Gate Work Trips Through trips Resident Day Trips Overnight Visitor Day Trips Day Visitor Trips Total Trips
E1_MtRose 889 245 1,987 625 3,991 6,849
E2_Spooner 1,716 786 4,297 1,352 8,424 14,859
E3_Kingsbury 721 86 1,717 540 3,401 5,743
E4_LutherPass 427 370 379 119 1,019 1,887
E5_EchoSummit 420 730 1,849 582 3,307 6,468
E6_CA89 1,552 129 2,341 737 5,206 8,413
E7_CA267 1,409 451 2,380 749 5,124 8,704
Total 7,134 2,797 14,950 4,704 23,338 52,923
Table 2: External trips by type and gate: Model
External Gate Work trips Through trips Resident DayTrips Overnight Visitor DayTrips Day Visitors Total Trips
E1_MtRose 1,134 259 1,438 284 4,146 7,261
E2_Spooner 1,576 700 5,444 1,798 4,912 14,430
E3_Kingsbury 910 94 2,198 678 2,414 6,294
E4_LutherPass 52 318 134 158 362 1,024
E5_EchoSummit 538 571 2,495 778 2,690 7,072
E6_CA89 1,198 139 1,613 520 4,002 7,472
E7_CA267 1,236 401 2,230 502 3,658 8,027
Total 6,644 2,482 15,552 4,718 22,184 51,580

The table above shows that the match between the target trips and modeled trips by external station and market segment is close. The details on the sub-model that was calibrated for each of the market segment is presented below.

Highway Validation

In the highway assignment the origin-destination trip demand matrix created from the demand models is assigned (loaded) on to the network. The primary output from the highway assignment step is the traffic flow on each roadway link, commonly referred to as the model volume. This section presents the comparison of the model volume against the roadway count obtained from the count databases of the transportation agencies - Nevada Department of Transportation and California Department of Transportation’s Caltrans Performance Measurement System (PeMS) Data. The counts obtained from transportation agencies did not cover some of the regions in the modeling area, especially west shore and east shore. To fill this missing gap, the count from StreetLight Data was used. The link ID for the roadway links where StreetLight Data was used are the following: 145,3068,12135,14493,622,4881,4077,14579,14499,2439. Table 3 presents the overall summary and Table 4 provides the link level detail.

Table 3 Highway validation statistic
Statistic Model Threshold
% RMSE Overall 31.1% Below 40%
Correlation Coefficient 0.93 At Least 0.88
Percent of Links Within Allowable Deviation 85.3% At least 75%

In Table 4 the first four columns are self-explanatory. The column Model Deviation is defined as the Abs(1-Model/Count). Max Deviation is based on criterion developed by 2010 RTP Guidelines. It defined maximum deviation that is acceptable for each link based on the observed count - the larger the observed count, the smaller the acceptable deviation. The last column compares the Model Deviation and the Max Deviation and notes whether the link satisfies the max deviation criterion or not.

Transit Validation

Transit assignment validation compares the observed transit boardings against the model assigned transit boardings. The table below shows the route level comparison and the overall comparison. The overall boardings are very close to the observed boardings; however, at route level there are substantial differences. Matching transit boardings at a route level is challenging problem in a regional model but can be improved by improving the transit network coding and making it consistent across the region, which will also involve updating the highway network. Walk access distance is a significant determining factor for transit use; making its representation more realistic and breaking down large TAZs along the transit use corridor will also help in modeling transit more accurately.

Table 5: Boardings by Route
Route Desc Target Boardings Model Boardings
20 64 8
23 158 146
30 2 0
50 355 18
53 139 268
267 - Highway 267 Route 115 38
53 - Late Night 31 58
53 - LTCC 139 134
89 - TART Hwy 89 Route 155 7
East Shore Express 114 0
ML - TART Mainline 304 1061
ML-WS 75 0
PM TART Night Service 66 122
Total 1715 1861

Vehicles Miles Travelled

Vehicle miles travelled (VMT) is the total distance travelled by all the vehicle trips in the model, it quantifies the amount of travel on a network. These trips are segmented by the following categories:

The VMT target was obtained from StreetLight Data. The target data for number of trips, VMT and the average trip distance for each of the trip categories can be seen in Table 6. The model summary is shown in Table 7. The average trip distance, the VMT and the number of trips match well for the II trips and EE trips. However, for the IE trips, the number of trips and VMT in the model output is marginally higher than the StreetLight Targets. The reason is that the highway count data suggested a higher volume (than Streetlight Data counts) along some of the external stations and the model was validated to those higher counts. During model validation, count data typically takes priority over other data sources such as VMT targets.

VMT Report

Table 6: Target Trip Totals, VMT and Mean Distance
TripCat Num Trips Total VMT Mean Distance
EE Trips 1,399 92,953 66.4
Inside the model area 62,574 44.7
Outside the model area 30,379 21.7
IE/EI Trip 44,543 1,975,821 44.4
Inside the model area 444,052 10.0
Outside the model area 1,531,769 34.4
II Trip 217,731 912,881 4.2
Total 263,673 2,981,655 11.3
Table 7: Model Trip Totals, VMT and Mean Distance
TripCat NumTrip Total VMT Mean Distance
EE Trips 1,269 88,658 69.9
Inside the model area 32,533 25.6
Outside the model area 56,124 44.2
IE/EI Trips 49,070 2,226,752 45.4
Inside the model area 571,109 11.6
Outside the model area 1,655,643 33.7
II Trips 170,212 803,523 4.7
Total 220,551 3,118,933 14.1

Table 8 and Table 9 below shows the target and model summary for the EI (and IE) trips segmented by short-distance external zone trips and long-distance external zone trips (the definition and classification of trips into short-distance and long-distance is described in detail in the report Create External Transportation Analysis Zones). Number of trips and the VMT for each category is compared. It can be observed from the table that the model outputs match the target data reasonably well.

Short and Long External Travel

Table 8: Target IE/EI Trips and VMT (Short vs. Long)
Gate Short-Distance Trips Short-Distance VMT Long-Distance Trips Long-Distance VMT
1 5,963 208,524 40 5,068
2 11,626 432,098 1,162 145,545
3 4,333 91,458 35 15,039
4 1,361 39,766 5 2,099
5 1,975 77,546 2,279 293,647
6 6,386 160,207 1,560 199,655
7 6,452 127,434 1,366 177,735
Total 38,096 1,137,033 6,447 838,788
Table 9: Model IE/EI Trips and VMT (Short vs. Long)
Gate Short-Distance Trips Short-Distance VMT Long-Distance Trips Long-Distance VMT
1 6,936 248,454 64 9,704
2 12,647 456,213 1,076 138,725
3 6,165 152,462 34 15,371
4 698 23,214 8 3,519
5 4,530 193,571 1,965 247,104
6 5,864 176,985 1,458 209,470
7 6,077 145,733 1,548 206,226
Total 42,917 1,396,632 6,153 830,119